Welding rod of copper



Patented Dec. 18, 1934 UNITED sTATss eATENrIoFFies No Drawing. Application April 6, 1934, Serial N0.719,408

' 2 Claims. (Cl. 219-8) It is well known that, by the simultaneous addition of silicon and tin, brass alloys become particularly suitable for casting purposes and that their tensile properties are substantially improved by this addition. 3

Hitherto this favourable effect'was in particular observed with alloys having a copper content of from 56 to 58%. Recently similar properties have also been ascertained for alloys for foundry purposes having a copper content of from to 56%.

Such alloys with a copper content of from to were hitherto successfully worked up into wires which are specially suitable for autogenous gas fusion welding. As is well known, a small addition of silicon prevents evaporation of the zinc, whilst tin fulfills the purpose of acting as deterrent of the formation of porous weld metal.

However, it was impossible hitherto, to produce an alloy of 50% Cu and 50% Zn in the shape of thin wires obtained by either drawing or pressing, without destroying their main properties which they otherwise possess.

The subject of the present invention is the production of welding wires 2 mm. or more in diameter of copper and zinc according to a special process, without nickel and with the addition of small quantities of tin and silicon. Satisfactory results were obtained with a wire of the composition varying between 50-54% copper, 50-46% zinc with Git-0.4% silicon and 0.5 1% tin, preferably, however, of an alloy with equal parts of copper and zinc with the above admixtures which can be worked up easily to 2 mm. diameter. The alloy is particularly suitable for welding purposes for which it offers special advantages. The addition of small quantities of silicon tin is effected only for the above mentioned known reasons.

Accordingly the technical improvement is based on the knowledge of pressing or drawing, by special processes, welding wires of 2 mm. diameter and more, which consist of an alloy of equal parts of copper and zinc. The addition of small quantities of silicon tin has nothing to do with the above process. It has no influence whatever on the drawing operation and solely fulfills the purpose of checking the evaporation of zinc and the formation of porous Weld metal during welding. The production by casting of welding rods from this kind of alloys, even of such small diameters is well known. The material obtained however is hard and brittle. 'A cast rod of this composition and of this small diameter breaks into fragments like spaghetti at} the--mere touch. This brittleness is inherentin the constitution of the copper-zinc alloy and depends on the chemical composition, 5 temperature of formationand mainly on the cooling processes. a

As hitherto it was not possible to produce useful welding rods from an alloy of 50 parts cop per and 50 parts zinc, the present invention must bear some special feature. Save for some slight peculiarity in the action during the freezing of a copper-zinc alloy, there is hardly left any uncertainty. Thus it is known, that the excessive hardness and brittleness of cast rods 1 of equal parts of copper-zinc are conditional upon the presence of more or less important quantities of gamma crystals. Reinglas, in his book Chemische Technologie der Legierungen, issue 1919, page 228, writes: At 50% (occurrence of the gamma constituents) the alloy becomes so hard and brittle that it no longer can be worked, only with a very high zinc content does the hardness again decrease.

The importance of increasing the zinc con tent of welding rods of customary quality of 56% and more of copper is undeniable, in respect of the welding operation manifestly by virtue of the lowering of the melting point associated therewith. Hence the endeavour to increase the zinc content of the rods by coating them with a thin layer of zinc in order to obtain in this manner the most eiiective composition from the technical point of view. As, however, the coating materially increases the cost of production, this remedy is of little interest.

The series of researches undertaken to solve this problem, gradually enabled views to be formed of the structure of solid solutions of copper and zinc; these served as a guidance and finally showed the way to success. As is well known, the beta crystal type predominates in alloys of equal parts of copper and zinc, yet at the usual rate of cooling it is not possible to avoid in practice apart from beta particles the presence of alpha and lastly some gamma constituents. The applicant therefore strove in resorting to special precautionary measures to prevent the formation during solidification of these gamma mixed crystals as much as pos- 50 sible, or to restrict same to a minimum. According to results of recent research work at a temperature below 470 C. the beta mixed crystal is made to undergo a transformation not yet clearly defined, passing into the crystal type beta, prime the physical properties of which differ materially from the beta type.

The applicant based his theory on this knowledge and the practical tests during which temperatures were kept as low as possible and very sudden cooling was allowed to take place, resulted in a change of condition of the material as is revealed by an improvement of its physical properties and enables it to be drawn or pressed to a diameter of 2 mm. On the basis of this special method of procedure the applicant believes he can assume that the alloy of equal parts of copper and zinc more accurately expressed as 50-54 parts of copper, balance zinc used by him for pressing and drawing, preferably possesses the crystalline type of the beta and beta, prime mixed crystals with a very dense structure.

The reddish-yellow lustrous new fractures of the wires thus obtained, differ anyhow considerably from the greyish-white appearance of the fractures of cast rods of the same composition. Naturally it is not claimed that these rods consist entirely of mixed crystals of the beta and beta, prime type, as gamma constituents are naturally also present. This is proved by their hardness and brittleness. The main fact, however, is that the brittleness has been reduced to such an extent, that the alloy can be drawn smoothly without breaking into splinters. Fracture only occurs upon bending over energetically.

The mechanical and physical values of the alloy 50% copper and 50% zinc under the above conditions are as follows:

Tensile strength per sq. mm about 45-50 kg.

Elongation (1-10d) do 12-18% Brinnell hardness do 130-150 Melting point do 870 C. Specific gravity do 8.35

By this fact the inventor substantiates the improvement upon and in comparison with the present state of the technical craft.

What I claim is:-

1. As a new article of manufacture a welding wire for the purpose set forth, consisting of substantially 50-54% Cu and substantially 46-50% Zn and of 0.54% Sn, and 03-04% Si, and of approximately three cornered crosssection.

2. As a new article of manufacture a welding wire for the purpose set forth, consisting of an alloy of a minimum of 0.5% and a maximum of 1% Sn, and a minimum of 0.3% and a maximum of 0.4% Si and the remainder of substantially equal parts of Cu and Zn.

OSKAR BRANDENBERGER. 

